Great contribution Jagmaster
By the way Zivouhr, actually Nintendo is planning on creating a 3d and a 2d metroid in the future, but I am here to tell you that Nintendo will more likely put the 3d metroid on the Wii U, and the 2d metroid for the 3DS, as typically the big 3d games go on the home consoles.
I suggest you pick up both the 3DS and the Wii U if you have the opportunity here, as the 3DS has plenty of good, traditional games, such as Pokemon, a 2D Mario which is NSMB2, and despite what people say about the NSMB, it is a stellar platformer that focuses on coins, so maybe not the best platforming a Mario game can give, but still good, it also has Ocarina of Time 3D, A Link Between Worlds (which I honestly like more than Ocarina of Time, shh, the Ocarina of Time legion may kill me if they find out, plus a Link Between Worlds is like A Link to the Past), and it has some more modern nintendo games, such as Super Mario 3D Land, arguably the best game on the system, definitely in the top 5, Luigi's Mansion Dark Moon, and Mario and Luigi Dream Team. Let's not forget Mario Kart 7 as well. Just remember that most likely if you are looking for 2d side-scrolling Metroid, the 3DS will probably have that one.
The Wii U on the other hand has plenty of good 2d games as well, Rayman Legends, Donkey Kong Tropical Freeze, which is the sequel to Donkey Kong Country Returns, and is like the original Donkey Kong Country games (in case you didn't know, I prefer small 2d levels, but if you love them long, DKC has some long levels for a 2d platformer, compared to Mario anyway), NSMBU, if you decide not to jump on the bandwagon, could arguably be the best 2d Mario game of all time, it is my favorite 2d mario (dear god, don't tell the SMB3, or SMW fans, or my head will be on a platter for sure). It also has plenty of good modern games such as Super Mario 3D World, Mario Kart 8, Monster Hunter 3 U, and many more in the future such as Hyrule Warriors and ssb4 are coming soon. Let me tell you though, the Wii U has the e-shop, which as of now, is the only source of getting Metroid Fusion and in the future, Metroid Zero Mission since the 3ds doesn't have GBA games. The Wii U eshop also has Metroid, maybe Metroid 2, I can't remember, and Super Metroid. Other good games are Shovelknight, and I hear Pushmo World is good too. Most likely, this system will be used to its max to make an almighty 3d metroid.